blob.h

#ifndef BLOB_H
#define BLOB_H
#include <memory>
#include <vector>

template<typename T> class Blob
{
public:
    typedef T value_type;
    typedef typename std::vector<T>::size_type size_type;

    Blob();
    Blob(std::initializer_list<T> il);

    template<typename It>
    Blob(It b, It e);

    size_type size() const {return data->size();}
    bool empty() const {return data->empty();}

    void push_back(const T& t) {data->push_back(t);}
    void push_back(T&& t) {data->push_back(std::move(t));}
    void pop_back();

    T& back();
    T& operator[](size_type i);

    const T& back() const;
    const T& operator [](size_type i) const;
private:
    std::shared_ptr<std::vector<T>> data;
    void check(size_type i, const std::string& msg) const;
};

template<typename T>
Blob<T>::Blob() : data(std::make_shared<std::vector<T>>()) {}

template<typename T>
Blob<T>::Blob(std::initializer_list<T> il) :
    data(std::make_shared<std::vector<T>>(il)) {}

template<typename T>
template<typename It>
BLob<T>::Blob(It b, It e): 
    data(std::make_shared<std::vector<T>>(b,e)) {}

template<typename T>
void Blob<T>::check(size_type i, const std::string& msg) const
{
    if (i >= data->size())
        throw std::out_of_range(msg);
}

template<typename T>
T& Blob<T>::back()
{
    check(0,"back on empty Blob");
    return data->back();
}

template<typename T>
const T& Blob<T>::back() const
{
    check(0,"back on empty BLob");
    return data->back();
}

template<typename T>
T& Blob<T>::operator [](size_type i)
{
    check(i,"subscript out of range");
    return (*data)[i];
}

template<typename T>
const T& Blob<T>::operator [](size_type i) const
{
    check(i,"subscript out of range");
    return (*data)[i];
}

template<typename T>
void Blob<T>::pop_back()
{
    check(0,"pop_back on empty Blob");
    data->pop_back();
}

#endif